参数类型 &#39;Future<xxx> &#39; 不能分配给参数类型 &#39;FutureOr<xxx> &#39; 颤振和飞镖

Question

This code works if I use String as the type, but not if I use a class.

Calling code:

Future<Card> getCard() {
    return Future.value(currPack.getCard());
  }

Here is the getCard method:

  Future<Card> getCard() async {
    return Card("a", "b");
  }

Here is the Card class:

class Card  {
  String question = "";
  String answer = "";

  Card(String question, String answer) {
    this.question = question;
    this.answer = answer;
  }
}

When I use the Card class, I get a warning message saying:

The argument type 'Future<Card>' can't be assigned to the parameter type 'FutureOr<Card>'

If I change the return type from Card to String and set the method to return a string it works fine.

Answer 1

Turns out there is a class in material design called Card: 'package:flutter/src/material/card.dart'.

The first bit of code is part of a screen that imports material.dart (import 'package:flutter/material.dart').

The other code is from a standalone class that doesn't import material.dart, but does reference the local card class (import 'package:flashcards/modules/Card.dart';).

So to sum it up: the error was caused by having references to two classes with the same name and not distinguishing between the two.